#include <iostream>
using namespace std;

class C1
{
    int m_A; // 默认是私有权限
};

struct C2
{
    int m_A; // 默认是公有权限
};

int main()
{
    C1 c1;
    // c1.m_A = 100;//错
    C2 c2;
    c2.m_A = 100;
    cout << "hellow world!" << endl;
    system("pause");
    return 0;
}
